Re: [PATCH 23/25] media: exynos4-is: fix pm_runtime_get_sync() usage count

[Jonathan Cameron]

On Wed, 5 May 2021 11:42:13 +0200
Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx> wrote:

> The pm_runtime_get_sync() internally increments the
> dev->power.usage_count without decrementing it, even on errors.
> 
> On some places, this is ok, but on others the usage count
> ended being unbalanced on failures.
> 
> Replace it by the new pm_runtime_resume_and_get(), introduced by:
> commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
> in order to properly decrement the usage counter, avoiding
> a potential PM usage counter leak.
> 
> As a bonus, such function always return zero on success. So,
> some code can be simplified.
> 
> Reviewed-by: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>

Might be nice to call out the two odd cases below.

> diff --git a/drivers/media/platform/exynos4-is/mipi-csis.c b/drivers/media/platform/exynos4-is/mipi-csis.c
> index 1aac167abb17..ebf39c856894 100644
> --- a/drivers/media/platform/exynos4-is/mipi-csis.c
> +++ b/drivers/media/platform/exynos4-is/mipi-csis.c
> @@ -494,7 +494,7 @@ static int s5pcsis_s_power(struct v4l2_subdev *sd, int on)
>  	struct device *dev = &state->pdev->dev;
>  
>  	if (on)
> -		return pm_runtime_get_sync(dev);
> +		return pm_runtime_resume_and_get(dev);
>  
>  	return pm_runtime_put_sync(dev);
>  }
> @@ -509,11 +509,9 @@ static int s5pcsis_s_stream(struct v4l2_subdev *sd, int enable)
>  
>  	if (enable) {
>  		s5pcsis_clear_counters(state);
> -		ret = pm_runtime_get_sync(&state->pdev->dev);
> -		if (ret && ret != 1) {
Perhaps add something to the description on this less common case?

> -			pm_runtime_put_noidle(&state->pdev->dev);
> +		ret = pm_runtime_resume_and_get(&state->pdev->dev);
> +		if (ret < 0)
>  			return ret;
> -		}
>  	}
>  
>  	mutex_lock(&state->lock);
> @@ -535,7 +533,7 @@ static int s5pcsis_s_stream(struct v4l2_subdev *sd, int enable)
>  	if (!enable)
>  		pm_runtime_put(&state->pdev->dev);
>  
> -	return ret == 1 ? 0 : ret;
> +	return ret;
>  }
>  
>  static int s5pcsis_enum_mbus_code(struct v4l2_subdev *sd,